What cosmetic condition is characterized by plugs formed in hair follicles?

The condition characterized by plugs formed in hair follicles is acne. Acne develops when hair follicles become clogged with excess oil (sebum), dead skin cells, and sometimes bacteria. This clogging can create comedones, commonly known as blackheads and whiteheads, which are the visible signs of acne. The inflammatory response due to the blockage can lead to redness, swelling, and the formation of pustules or cysts, resulting in the common observable symptoms of acne on the skin.

In contrast, melanoma refers to a type of skin cancer that originates in melanocytes, the cells that produce melanin, and is not related to hair follicles. Eczema is a chronic inflammatory condition of the skin characterized by dry, itchy patches, but it does not involve clogged hair follicles. Psoriasis is another skin condition that results in red, scaly patches, often linked to an overactive immune system response, and similarly does not involve the plugging of hair follicles like acne does.

Therefore, the defining feature of acne is the plugging of hair follicles, making it the correct answer.